The proposed project will examine the effects of adrenergic drugs on ocular hydrodynamics. In the case of adrenergic agonists with strong alpha-adrenoceptor activity, the effect on intraocular pressure (IOP) is biphasic: a transient rise in IOP followed by long-lasting fall in IOP. In contrast, acute doses of agonists with predominantly beta-adrenoceptor activity produce a monophasic lowering of IOP in normotensive and hypertensive eyes. Interestingly, the chronic administration of beta-adrenergic agonists can produce a rise in IOP on the second and subsequent days of consecutive topical administration. Relatively selective beta-adrenoceptor agonists and antagonists will be used, alone and in combination, to: 1) evaluate the dose-response activities of agonists and antagonists in normotensive and hypertensive eyes of rabbits; 2) elucidate the nature of the beta-adrenoceptor primarily responsible for alteration in hydrodynamics; 3) determine changes in biochemical correlates in aqueous during the action of beta-adrenoceptor agonists and antagonists; and 4) investigate the effects of beta-adrenergic drugs on circadian oscillations in IOP. This project should provide a more complete understanding of the role of beta-adrenoceptors in modulating hydrodynamics and metabolism in the eye and a more rational basis for the potential use of selective beta-adrenergic drugs in controlling glaucoma.